There has been known an acoustic wave device in which a first piezoelectric substrate having a comb-shaped electrode is bonded to a first surface of a support substrate and a second piezoelectric substrate having no comb-shaped electrode and of which the material and the crystal axis orientation are the same as those of the first piezoelectric substrate is bonded to a second surface of the support substrate to reduce the warpage of the substrate due to the temperature change as disclosed in, for example, Japanese Patent Application Publication No. 2010-200197. In addition, there has been also known an acoustic wave device in which the directions of the electrode fingers of acoustic wave resonators located on both surfaces of a piezoelectric substrate are made not to be parallel to each other to reduce the deviation of the center frequency as disclosed in, for example, Japanese Patent Application Publication No. 11-136081. There has been also known an acoustic wave device in which an acoustic wave resonator is formed on each of piezoelectric thin films located on both surfaces of a substrate as disclosed in, for example, Japanese Patent Application Publication No. 2007-60465.
When acoustic wave resonators each including an Interdigital Transducer (IDT) are located on the principal surface of a piezoelectric substrate, a bulk wave generated from one of the acoustic wave resonators may be reflected by the lower surface of the piezoelectric substrate and enter another acoustic wave resonator, deteriorating the characteristics. Additionally, when acoustic wave resonators are located on both principal surfaces of the piezoelectric substrate, a bulk wave generated from the acoustic wave resonator located on a first principal surface of the piezoelectric substrate may pass through the piezoelectric substrate and enter the acoustic wave resonator located on a second principal surface, deteriorating the characteristics.